In the study of sustained-release implants, the choice of biodegradable materials is essential. Polylactic acid is a kind of polymer with excellent biocompatibility and degradability, the final products of metabolism in the body are water and carbon dioxide, and the intermediate lactic acid is also a normal sugar metabolite in the body, does not accumulate in organs, and it is a medical excipient approved by the State Drug Administration. In order to ensure the compatibility of the drug, the implant coating is prepared by using the same or similar material as the sustained-release matrix, but the viscosity of the polylactic acid is very high, and the “wet” implants that have just been soaked in the coating solution adhere to each other, meantime destroy the yield of the coating, and it is not suitable for the coating operation. For example, Chinese patent CN200610152903.7 discloses a long-acting sustained-release preparation of naltrexone, which uses polylactic acid to coat naltrexone microspheres, and Chinese patent CN201110457641.6 discloses a long-acting naltrexone implant, the naltrexone microspheres after compression were also coated with DL-polylactic acid. However, as mentioned above, since the viscosity of polylactic acid is too high, the contact between the microspheres or the tablets after the coating, or the contact of the microspheres or tablets after the coating with the bottom surface of the tray during drying may cause the surface of the envelope film to adhere and rupture, affecting the integrity of the drug may cause the surface of the coating to adhere and rupture, affecting the integrity of the drug.
In the traditional process, in order to achieve the coloring, gastric dissolution, enteric dissolution, sustained release, controlled release and other effects of the tablets, the non-stick coating material is used, and the coating of the non-stick material can be coated in a spray-drying manner in the coating pool. However, the long-acting sustained-release drug is made of polylactic acid, which has a large viscosity. Many tablets are coated in one container at the same time, which inevitably causes the tablets to stick together.
At present, the research on the implant coating and the public literature technology are laboratory-level preparation processes, which cannot be mass-produced. Among them, many influencing factors and conditions obtained for screening are not applicable in large-scale production, this is because the active ingredients of the microspheres are different, the way of adding the internal phase emulsion to the external phase solution is different, the composition of the solution is different, and the specific excipient ingredients used are different, which will lead to the unpredictable changes of the preparation process conditions. Therefore, it is necessary to re-examine the study in order to obtain the ideal sustained release implant with a sustained release effect and a therapeutic effect.
Chinese patent (a coating device for slow release fertilizer: CN201810333180.3) discloses a coating device for slow release fertilizer comprises a supporting device and a coating mechanism mounted on the supporting device; the coating mechanism comprises a coating cylinder and a feeding funnel fixed at an upper end of the coating cylinder; a screen is fixed on a circumferential inner surface of the coating cylinder, and a discharge slot is provided at a joint between the screen and the side wall of the coating cylinder; the side wall surface of the coating cylinder is provided with a circular hole which cooperates with the spray pipe, and the spray pipe penetrates the side wall of the coating cylinder through the circular hole; and a heating tube is fixed to an inner surface of the wall of the coating cylinder. Although the coating device of the patent has a simple structure, the patent uses a spray pipe for coating, and it is impossible to uniformly spray the viscous coating solution, which may cause adhesion of the implant tablet to the wall of the coating cylinder, and the coating is incomplete and uneven, and the thickness of the slow-release fertilizer after the coating is not uniform, resulting in uneven release performance, which increases the cost.